Revert "IR: Specify underlying type instead of r226570, NFC"

This reverts commit r226571.  GCC really doesn't like it [1].

[1]: http://bb.pgr.jp/builders/cmake-llvm-x86_64-linux/builds/20260

llvm-svn: 226579

llvm/include/llvm/IR/Metadata.h

@@ -48,10 +48,10 @@ class Metadata {
 
 protected:
   /// \brief Active type of storage.
-  enum StorageType : unsigned char { Uniqued, Distinct, Temporary };
+  enum StorageType { Uniqued, Distinct, Temporary };
 
   /// \brief Storage flag for non-uniqued, otherwise unowned, metadata.
-  StorageType Storage : 2;
+  unsigned Storage : 2;
   // TODO: expose remaining bits to subclasses.
 
   unsigned short SubclassData16;